Fluid pressure control mechanism



Feb. 18, 1947. E. R. FITCH 2,416,091

FLUID PRESSURE CONTROL MECHANISM y Filed Aug. 2:, 1943 I 95 is: a 2

Patented Feb. 18, 1947 Ellery R. Fitch, Elyria, Ohio, assignor to Bendix- Westinghouse Automotive Air Brake Company, Elyria, Ohio, a corporation of Delaware i 4 Application August 23, 1943, Serial No. 499,683

, 2 Claims. (Cl. 137-144) This invention relates primarily to fluid pressure control mechanism and more particularly to fluid pressure control mechanism for the brakes of an airplane.

It has previously been proposed to Provide, in connection with an airplane equipped with hydraulic' brakes oi more or less conventional type, a separate or auxiliary fluid pressure supply such as compressed air for operating the brakes in the event of failure of the hydraulic system, the flow of fluid pressure from the emergency supply being controlled by means of a brake valve 10- cated adjacent the operator. In systems of this type, and particularly in systems wherein diifer- A further object of the invention is to pro vide,- in a system of the above type, valvular means of the so-called double check valve type so constituted as to isolate one of the fluid pressure sources from the other. v

A still further object. of the invention is to provide, ,in connection with a system of the above type, adouble check valve for normally maincylinders 4 are connected to brake levers 5 taining a connection between the source ofhydraulic fluid and the actuator, and for permitting communication to be established between the auxiliarysource of'fluid pressure and the actuator at the will of the operator.

Yet another object of the invention is to provide, in a double check valve of the above type, means for insuring positive operation of the valve mechanism to connect the auxiliary source with the actuator at the will of the operator regardless of the pressure being supplied to the actuator from the primary source.

These and other objects and novel features of the invention will appear more fully hereinafter from the following detailed description when taken in connection 'with the accompanying drawing. It is to be expressly understood, however, that the drawing is empioyed for purposes of illustration only, and is not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawing, the invention isillustrated in connection with a brake system for an airplane,

through piston rod 8, and are adapted to be supplied with fluid pressure from a hydraulic master cylinder 1 or conventional type, the piston of the master cylinder being actuated by means of a brake pedal 8 having a pivotal connection 9 with a piston rod in of the master cylinder. An auxiliary source of fluid pressure includes a reservoir ll supplied with fluid pressure by a compressor, not shown, through a conduit II, the flow of fluid pressure from thereservoir being controlled by means of a control valve I 3 connected thereto by means of a conduit II. The master cylinder is connected 'with the actuators through a conduit IS, a double check valve [8, to be described hereinafter, a, conduit I1 and a conduit III, while the control valve I3 is connected with the brake actuators through a conduit 19, the valve I6, and conduits l1 and ID.

The control valve [3 may preferably beconstructed in accordance with the principles set forth in the patent to William J. Andres and Roy S. Sanford, No. 2,133,275, dated October 18, 1938.

This valve i provided with a casing 20 having an operating pedal 2| pivotally mounted thereon by means of a pivot pin 22, and is provided with an exhaust conduit 23, and it will be understood.

I8 to establish a pressure in the'latter conduit substantially proportional to the degree of movement of the control pedal. Thus in the embodiment shown, power operation is available under the control of the valve 13 while manual opera- J tion of the brakes is available by operation o'fu' the brake pedal 8.

As illustrated in the drawing, the doublecheclr valve i provided with a casing 24, the left end of the casing being provided with an inlet chamber 25 having a connection with the conduit 15 leading to the hydraulic master cylinder. A partition 28 is provided at the right end of the chamber, and serves to define, in connection with the casing, an outlet chamber'l'l, the partition being provided with a centrally located port 28 for permitting communication between the chambers.-

The flow of fluid through the port is controlled not shown, wherein a pair of brake actuators or 68 by means of a valve 28, the valve being provided v r n 3 with a stem 30 and a second valve 3| carried by the right end of the valve stem, the assembly thus formed being urged to the right by means of a valve spring 32 interposed between the right face of the partition 28 and the left side of the valve 3|. The valve assembly is thus adapted for movement in one direction under the action of the spring 32, movement in the other direction being controlled by means of. a valve operating element 33 slidably mounted in a bore 34 formed in the housing at the right end of the bore 34,

and communication between the bore 36 and the chamber 31 is eifected by means of ports 33 formed in the wall of the bore. The right end of the chamber is closed by means of flexible diaphragm 39 clamped at its outer periphery between the rightend of the casing and a cover plate 40 and attached at its center to the valve operating element 33 by means of a suitable washer 4| and a nut 42. The diaphragm acts in conjunction with the cover 40 to form an atmospheiic chamber 43 at the right side of the diaphragm, and the latter chamber is connected to atmosphere by means of a vent 44 in the cover. The valve operating element is normally maintained'in the position shown by means of a relatively heavy spring 45 interposed between stantially proportional to the degree of depression of the brake pedal. Since the diaphragm 39 is designed to have a relatively large area, it

' will be seen that the application of arelatively small pressure to the inlet chamber 31 will be 7 suflicient to overcome the tension of the spring 45 sufliciently to permit movement of the diaphragm and the valve operating element 33 to the right to allow movement of the valve 29-t o port closing position under the action of the spring 32. Thus the valve 29 will be moved to closed position during initial movement of the valve operating element to the right, subsequent movement of the element serving to move the left :end of the bore 36 away from the valve 3| to permit communication between the inlet chamber 31 and the outlet chamber 21 through ports 38 and bore 36, whereupon fluid pressure will be supplied'to the actuators through the chamber 21 and c nduits i1 and i8 at the pressure established in the inlet chamber 31. Stops 48 are provided in the the cover and the washer 4|, the spring 45 being of suflicient tension to overcome the tension of the valvespring 32 and to normally maintain the valve operating element in the position shown, a shoulder 46 formed thereon being maintained in engagement with stops 41.

It will be understood from the foregoing description that with the parts of the valve 16 in the position shown, operation of the brake pedal 3 to compress fluid in the master cylinder will serve to supply fluid under pressure to the actuators throughconduit l5, inlet chamber 25, port 28, outlet chamber '21;- and conduits i1 and I8, the passage of fluid from the chamber 21 intothe inlet chamber 31 and into the conduit i9 being prevented by the action of the valve 3| in closing the left end ofthe bore 36 in the valve operating element, itbeing understood that the spring 45 is also so tensioned as to prevent movement of the valve operating element and diaphragm to the right in response to the action of fluid pressure on the area of the valve operating element at the left side of the seal 35. Since the spring 45 is so tensioned as to maintain the parts in the position shown regardless of the degree of fluid pressure supplied to the chamber-21, it will be understood that release of the brakes will be efcover member 40, these stops being adapted to engage the right side of the washer 4| in order toprevent excessive movement of the diaphragm to the right with a resultant tendency toward distortion and rupture of the diaphragm, and on further operation of the brake valve i3 to increase the pressure of fluid supplied tothe actuators, the washer 4| will be maintained against the above stops and continuous communication will be maintainedbetween the inlet chamber 31. .and the outlet chamber 21. On operation of the brake valve to release fluid pressure from the actuators, fluid pressure will be released through conduits l1 and I3, outlet chamber 21,-the bore 36, ports 39, inlet chamber 31, conduit |9,- the valve 3 and the exhaust conduit 23. Since the tension of the spring is relatively light compared with the fluid pressureexerted on the area of the diaphragm 39, the passage between chamhers 21 and 31 will remain open until the pressure in chamber 31 is reduced to a comparatively low value, whereupon the valve operating element will be moved to the left under the action of the spring 45, this serving to close the end of the 1 bore 36 and subsequently move the valve 29 to fected onrelease operation of the brake pedal 8 withoutchanging the relationship'of the parts in the valve mechanism |6.

In the event the operator is desirous of supplying fluid pressure to the actuators from the reser-- 'voir II. it will be apparent that on depression of the pedal iii, the valve mechanism l3 will be effective to dis-establish communication between conduits l9 and 23 and to establish communication between conduits I4 and I9, whereupon fluid pressure will be supplied to the conduit l9, and therefore to the inlet chamber 31 to which the conduit is connected, at a pressure which is subthe position shown in the drawing. prevent leakage of pressure fluid from thecham ber 21 to the chamber 25 when the actuators are,

being supplied with fluid from the reservoir H, the valve spring 32 is sufllclently tensioned to maintain the valve 29 in closed position against any operating pressure obtaining in the outlet ervoir II and the actuators at will, regardless of the pressure beingsupplied to the actuators by the operation of the master cylinder. The system is thus eifective to segregate the fluids in the two portions of the system, and is likewise effective to prevent the entrance of air or other gas into the hydraulic portion of the system in. the event a partial vacuum is formed in that portion of the system during release operation of the brake pedal .8, as may occur under certain conditions of operation of a system of this type. It 'is also to be noted that the valve mechanism I6 may be equally effective to normally prevent intermixlng of the fluids in the two portions of the system re gardless of the type of fluids being used, it being In order .to 1

' to those-skilled that different gases may. likewise be utilized in different portions of the system.

While the invention has been illustratedand cationxbetween said second inlet chamber and described herein with considerable particularity,

outlet chamber, a valve for controlling communioutlet chamber, means rigidly connecting said valves to eachother, a valve operating element having a boreconnected' with the second inlet chamber at one end and adapted at its other end to engage the second named valve to prevent communication between the second inlet chamber having first and second inlet chambers and an outlet chamber, a valve for controlling communication between the first inlet chamber and the outlet chamber, a valve for controlling communication between said second inlet chamber and outlet chamber, means. rigidlyconnecting said valves to each other, a valve operating element having a bore connected with the second inlet chamber at one end and adapted at its other end to engage the second named valve to prevent communication between the second inlet chamber and the outlet chamber on movement of said element in one direction and to disengage the second named valve to permit communication between the second inlet chamber and the outlet chamber on movement of the element in the other direction, a spring for moving the first named valve to closed position on movement of the element in said other direction, a stronger spring interposed between said casing and element for biasing the latter in said one directi n to overcome the force exerted by the first named spring to normally maintain the first named valve in open position, means responsive v to the pressure in said second inlet chamber for moving the element in the said other direction when the pressure in said chamber exceeds a predetermined value to permit closing of the first named valve, said rigid connection between said valves providing means whereby the valves are positively sequentially operated in response to movement of said element to prevent communication between the outlet chamber and both inlet chambers at the same time and whereby positive disengagement of the second named valve with said other end of the bore in said element is effected on movement of the latter in said other direction when the first named valve is in closed position.

2. A double check valve comprising a casing having first and second inlet chambers and an outlet chamber, a valve for controlling communication between the first inlet chamber and the ment for biasing the and the outlet chamber on movement of said element in one direction and to disengage the second named valve to permit communication between the second inlet chamber and the outlet chamber on movement of the element in the other direction, a springfor moving the first named valve to closed position on movementot engagement of the second named valve with said other end of said bore in said element is effected on movement of the latter in said other direction when the first. named valve is in closed position;

ZELLERY a. moth,

Ruminations orrnn The following references are of record in the file of this patent:

UNITED STATES PATENTS I I Number Name Date 2,240,166 Stanley Apr. 29, 1941 2,275,255 Freeman Mar. 3, 1942 2,336,887 Piron Dec. 14, 19 3 2,313,991 Fitch Mar. 16, 1943 2,132,090 Vorech Oct. 4, 1938 2,380,507 Eaton July 31, 1945 2,200,830 Beharrell May 14, 1940 2,320,763 Trautman June 1, 1943 1,508,938 Powers Sept. 16, 1824 1,707,742 Schiolm Apr. 2. 1

v exerted by the first named spring to normally maintain the in open position, a flexible diaphragm connected with said element and responsive to the pressure communication be- I tween the outlet chamber and bers at th same time and whereby positive dis-n 

